Outside the Box – Air Travel and Disease

According to researchers at Tufts University, over 1 billion travelers fly annually and 50 million of these make treks to developing countries. And while it is infrequently reported and difficult to assess, there is a risk of disease transmission from these frequent travels. Ever been stopped for trying to bring foreign fruit back to the USA? Or traveled in a country with a recent outbreak of diseases such as H1N1 (swine flu)? If so, you risk the possibility of detainment for quarantine as did travelers from India a few years ago.

So what is it about airline cabins that make them hotbeds for the possible transport of communicable disease? It is due to their design as a ventilated and enclosed environment. Airline cabins expose passengers to hypobaric hypoxia (a condition that affects the body’s ability to transfer oxygen from the lungs to the bloodstream), dry humidity (which can cause your nasal passages and throat to crack, allowing receptor points for disease to enter), and when coupled with the close proximity of passengers, it allows for the easy spread of airborne diseases.

The Hartsfield-Jackson Atlanta International Airport is the busiest in the United States. Though New York/New Jersey’s cluster of airports services the most for a metro-regional area, Atlanta is the single most productive in turnover of passengers at nearly 46 million in 2012. Makes you wonder how many colds and flues were spread through that massive delivery of people, no? Image captured June 10, 2011 by the 50-cm satellite WorldView-2, and comes courtesy of DigitalGlobe. Photo enhanced by Apollo Mapping.

Most commercial airlines recirculate 50% of their air through high-powered HEPA filters, and while this allegedly removes 99.97% of harmful particles, there has been rising concern about the accuracy of these claims. A panel was formed in 2000 to study these claims, and in 2004, the Aviation Health Working Group undertook a study that assessed factors such as humidity, temperature, air speed and concentrations of carbon monoxide, carbon dioxide and microbiological flora as contributors to the spread of disease. Large droplet and airborne mechanisms were found to be the greatest risk factors, largely due to the high density and closeness of passengers.

Diseases that fall under the category of large droplet and airborne contagions include tuberculosis (TB), SARS and Meningococcal disease. The largest incident of TB transfer was from a flier who traveled from Baltimore to Chicago and then on to Honolulu. Four of fifteen passengers seated within two rows of the contagious flyer tested positive during tuberculin skin tests. SARS is a non-typical pneumonia which is believed to be spread through aerosolized droplets from either direct or indirect contact. During the Amoy Gardens outbreak in Hong Kong, 40 flights were investigated for possible SARS transmission. One flight, a 3-hour trek from Hong Kong to Beijing in 2003, accounted for 22 of 37 fliers that tested positive for SARS. This was somewhat different than the TB example, as the flight was less than 8 hours, and those affected were as far away as seven rows, compared to two with the TB case. For meningococcal disease, transmission is considered in cases where the patient has been on a flight over eight hours within a two-week period. The US Center for Disease Control recorded twenty-one suspected cases in the time period between 1999 and 2001. Other diseases that have been studied are the common cold and influenza, both of which have been reported or suspected in high amounts.

Conclusions from the study were recognition of the right and ability for airlines to prevent suspected travelers carrying communicable diseases from boarding the plane, but that solution was deemed impractical. The researchers stressed the importance of hand-washing and good hygiene as critical to the suppression of disease transmission, and masks were suggested for travelers showing signs of communicable disease.

A report from Fox News states that the aforementioned HEPA filters are not mandatory and as many as 15% of commercial airlines that carry more than 100 passengers do not have the filtration systems installed. The report also states that older systems in place when smoking was allowed on planes used 100% fresh air, significantly lowering the likelihood of disease transmission. So as the rage for retro everything goes on in the fashion world, should there be a return to the airline filtration systems of the past used in tandem with these HEPA filters to minimize the risk of disease transmission? The jury is out, but the research continues.